There is an interest in various types of agricultural work in detecting the proportion of certain content substances in samples by sensing means. In addition to crop material, possible samples also include soil samples, liquid manure and milk. The detected content substances can be used to assess the sample (particularly crops or other agricultural products) monetarily, or the sensed values are saved for purposes of precision agriculture, e.g. for customized fertilizer application, or they can be used for controlling application amounts, for example from a liquid manure tank.
A customary technique for determining content substances in the agricultural field is near-infrared spectroscopy, in which broadband light is applied to the sample and the light reflected from or transmitted by the sample is decomposed spectrally and analyzed. Measuring heads based on such technology are described in DE 199 22 867 A1, WO 01/31304 A1 and DE 10 2004 048 103 A1 for example. They use a dispersive element (prism or grating) for spectral decomposition of the light and a light detector to be able to sense the individual wavelengths simultaneously. These measuring heads use movable elements for moving a white standard into the beam path to provide a reference.
One problem addressed by the invention is providing a spectroscopic measuring head that requires fewer movable elements for providing a reference.